Certain pulverulent chemical products which come in bags give off dust when the bag is being emptied. This dust is likely to be inhaled and certainly inconveniences the operators. To limit this risk, the operators have therefore to wear breathing masks and anti-dust attire.
This problem is encountered both for water-soluble products and for water-insoluble products.
Chemical products of this type are, for example, the polyacrylamides used as flocculants in water treatment. These polymers may be:                anionic and used in the treatment of drinking water and of mineral substances (quarries, truck washes, mines, etc),        cationic and used in the treatment of urban sludge for example, with dust which is an irritant.        
When the quantities are large, the pulverulent products are transported in trucks or in big bags, which has led to the development of special installations.
However, for smaller quantities, such means are unsuitable. As far as the applicant is aware, there does not currently exist any suitable installation apart from a few low-quality devices. Aside from the abovementioned problem associated with the inhalation of dust by the operator, it is found that a non-insignificant amount of the dust may be deposited on the ground, and become hydrated, making the surrounding surfaces slippery and dangerous.
In spite of everything, certain solutions have been proposed. One of these involves ventilating the zone in which the bag is emptied and then filtering the dusty air. However, and particularly in the case of hygroscopic or plugging products, the filter sleeves very soon become plugged, making the system ineffective.
It is therefore necessary to develop a system for emptying bags of pulverulent material which is suitable, for example, for small purification stations. It needs in particular to be effective and economical, and require the minimum of maintenance